The autoregulatory HspR repressor protein governs chaperone gene transcription in Helicobacter pylori

In the present study, we provide evidence that the groESL, hrcA-grpE-dnaK a nd cbpA-hspR-orf operons encoding the major chaperones of the human gastric pathogen Helicobacter pylori are transcribed by the vegetative sigma facto r sigma(80) and are regulated negatively by the transcriptional repressor H spR. In vitro studies with purified recombinant HspR protein established th at the protein represses transcription by binding to large DNA regions cent red around the transcription initiation site in the case of the P-cbp promo ter, and around -85 and -120 in the case of the P-gro and P-hrc promoters r espectively. All three binding sites contain DNA motifs with some similarit y to the HAIR sequence identified as a consensus for the HspR protein of St reptomyces. In contrast to the situation in Streptomyces, in which transcri ption of HspR-regulated genes is induced in response to heat shock, transcr iption of the HspR-dependent genes in H. pylori is not inducible by thermal stimuli. Transcription of the groESL and cbpA-hspR-orf operons is induced by osmotic shock, while transcription of the hrcA-grpE-dnaK operon, althoug h HspR dependent, is not affected by salt treatment. The possibility that H spR could constitute a global transcriptional regulator for diverse cellula r functions with implications for pathogenesis is discussed.